1#ifndef SCATTERLIST_H
2#define SCATTERLIST_H
3#include <linux/kernel.h>
4
5struct scatterlist {
6	unsigned long	page_link;
7	unsigned int	offset;
8	unsigned int	length;
9	dma_addr_t	dma_address;
10};
11
12/* Scatterlist helpers, stolen from linux/scatterlist.h */
13#define sg_is_chain(sg)		((sg)->page_link & 0x01)
14#define sg_is_last(sg)		((sg)->page_link & 0x02)
15#define sg_chain_ptr(sg)	\
16	((struct scatterlist *) ((sg)->page_link & ~0x03))
17
18/**
19 * sg_assign_page - Assign a given page to an SG entry
20 * @sg:		    SG entry
21 * @page:	    The page
22 *
23 * Description:
24 *   Assign page to sg entry. Also see sg_set_page(), the most commonly used
25 *   variant.
26 *
27 **/
28static inline void sg_assign_page(struct scatterlist *sg, struct page *page)
29{
30	unsigned long page_link = sg->page_link & 0x3;
31
32	/*
33	 * In order for the low bit stealing approach to work, pages
34	 * must be aligned at a 32-bit boundary as a minimum.
35	 */
36	BUG_ON((unsigned long) page & 0x03);
37#ifdef CONFIG_DEBUG_SG
38	BUG_ON(sg->sg_magic != SG_MAGIC);
39	BUG_ON(sg_is_chain(sg));
40#endif
41	sg->page_link = page_link | (unsigned long) page;
42}
43
44/**
45 * sg_set_page - Set sg entry to point at given page
46 * @sg:		 SG entry
47 * @page:	 The page
48 * @len:	 Length of data
49 * @offset:	 Offset into page
50 *
51 * Description:
52 *   Use this function to set an sg entry pointing at a page, never assign
53 *   the page directly. We encode sg table information in the lower bits
54 *   of the page pointer. See sg_page() for looking up the page belonging
55 *   to an sg entry.
56 *
57 **/
58static inline void sg_set_page(struct scatterlist *sg, struct page *page,
59			       unsigned int len, unsigned int offset)
60{
61	sg_assign_page(sg, page);
62	sg->offset = offset;
63	sg->length = len;
64}
65
66static inline struct page *sg_page(struct scatterlist *sg)
67{
68#ifdef CONFIG_DEBUG_SG
69	BUG_ON(sg->sg_magic != SG_MAGIC);
70	BUG_ON(sg_is_chain(sg));
71#endif
72	return (struct page *)((sg)->page_link & ~0x3);
73}
74
75/*
76 * Loop over each sg element, following the pointer to a new list if necessary
77 */
78#define for_each_sg(sglist, sg, nr, __i)	\
79	for (__i = 0, sg = (sglist); __i < (nr); __i++, sg = sg_next(sg))
80
81/**
82 * sg_chain - Chain two sglists together
83 * @prv:	First scatterlist
84 * @prv_nents:	Number of entries in prv
85 * @sgl:	Second scatterlist
86 *
87 * Description:
88 *   Links @prv@ and @sgl@ together, to form a longer scatterlist.
89 *
90 **/
91static inline void sg_chain(struct scatterlist *prv, unsigned int prv_nents,
92			    struct scatterlist *sgl)
93{
94	/*
95	 * offset and length are unused for chain entry.  Clear them.
96	 */
97	prv[prv_nents - 1].offset = 0;
98	prv[prv_nents - 1].length = 0;
99
100	/*
101	 * Set lowest bit to indicate a link pointer, and make sure to clear
102	 * the termination bit if it happens to be set.
103	 */
104	prv[prv_nents - 1].page_link = ((unsigned long) sgl | 0x01) & ~0x02;
105}
106
107/**
108 * sg_mark_end - Mark the end of the scatterlist
109 * @sg:		 SG entryScatterlist
110 *
111 * Description:
112 *   Marks the passed in sg entry as the termination point for the sg
113 *   table. A call to sg_next() on this entry will return NULL.
114 *
115 **/
116static inline void sg_mark_end(struct scatterlist *sg)
117{
118#ifdef CONFIG_DEBUG_SG
119	BUG_ON(sg->sg_magic != SG_MAGIC);
120#endif
121	/*
122	 * Set termination bit, clear potential chain bit
123	 */
124	sg->page_link |= 0x02;
125	sg->page_link &= ~0x01;
126}
127
128/**
129 * sg_unmark_end - Undo setting the end of the scatterlist
130 * @sg:		 SG entryScatterlist
131 *
132 * Description:
133 *   Removes the termination marker from the given entry of the scatterlist.
134 *
135 **/
136static inline void sg_unmark_end(struct scatterlist *sg)
137{
138#ifdef CONFIG_DEBUG_SG
139	BUG_ON(sg->sg_magic != SG_MAGIC);
140#endif
141	sg->page_link &= ~0x02;
142}
143
144static inline struct scatterlist *sg_next(struct scatterlist *sg)
145{
146#ifdef CONFIG_DEBUG_SG
147	BUG_ON(sg->sg_magic != SG_MAGIC);
148#endif
149	if (sg_is_last(sg))
150		return NULL;
151
152	sg++;
153	if (unlikely(sg_is_chain(sg)))
154		sg = sg_chain_ptr(sg);
155
156	return sg;
157}
158
159static inline void sg_init_table(struct scatterlist *sgl, unsigned int nents)
160{
161	memset(sgl, 0, sizeof(*sgl) * nents);
162#ifdef CONFIG_DEBUG_SG
163	{
164		unsigned int i;
165		for (i = 0; i < nents; i++)
166			sgl[i].sg_magic = SG_MAGIC;
167	}
168#endif
169	sg_mark_end(&sgl[nents - 1]);
170}
171
172static inline dma_addr_t sg_phys(struct scatterlist *sg)
173{
174	return page_to_phys(sg_page(sg)) + sg->offset;
175}
176
177static inline void sg_set_buf(struct scatterlist *sg, const void *buf,
178			      unsigned int buflen)
179{
180	sg_set_page(sg, virt_to_page(buf), buflen, offset_in_page(buf));
181}
182
183static inline void sg_init_one(struct scatterlist *sg,
184			       const void *buf, unsigned int buflen)
185{
186	sg_init_table(sg, 1);
187	sg_set_buf(sg, buf, buflen);
188}
189#endif /* SCATTERLIST_H */
190